1. Field of the Invention
The present invention relates to a water-cooled internal combustion engine cooled by cooling water and, more specifically, to water jackets formed in the cylinder block and the cylinder head of a water-cooled internal combustion engine. The internal combustion engine is intended to be incorporated into, for example, an outboard motor.
2. Description of the Related Art
There has been known a water-cooled internal combustion engine for an outboard motor, which has a cylinder block provided with an exhaust manifold passage in which exhaust gas discharged from a plurality of combustion chambers through exhaust ports collects and which has water jackets formed around the exhaust manifold passage. Such a water-cooled internal combustion engine is disclosed in, for example, Japanese Patent Application Publication No. 10-220283.
When the exhaust manifold pass age is formed in the cylinder block, the inlet to the exhaust manifold passage is formed in the joint surface of the cylinder block so as to extend along the arrangement of cylinders to connect the exhaust manifold passage respectively to the exhaust ports of the combustion chambers. When the cylinder head is joined to the joint surface of the cylinder block, parts of the cylinder head around the inlet to the exhaust manifold passage need to be fastened to the cylinder block with many bolts to seal the inlet of the exhaust manifold passage. Use of many bolts to fasten the cylinder head to the cylinder block requires much assembling work and increases the cost. If the water jackets formed around the exhaust manifold passage are divided into parts by those bolts, the water jackets cannot bring their cooling ability into full play.